The present invention relates to a device for determining the position of a moving part, particularly to a device containing a sensor carried by the moving part and designed to supply two out-of-phase signals, each assuming alternately the value 0 or 1 as the sensor is carried in one or the other direction.
Sensors of this type, generally involving a glass disk printed with opaque sections and rotated by the moving part between an electroluminescent diode, made out of gallium arsenide for example, and a phototransistor connected to a threshold amplifier that detects the transition from a transparent to an opaque zone, are known.
This type of sensor has a drawback in that, when the speed of rotation is very slow and the disk is more subject to vibration, anomalies will appear. Actually, when the position of the disk is such that the electroluminescent diode is at the transition from a transparent zone to an opaque zone, the threshold amplifier tends to oscillate, resulting in additional pulses that contaminate the results.
The present invention is intended to avoid this problem by using the fact that the two signals are out of phase and that, consequently, when one of the signals tends to oscillate because the associated electroluminescent diode is at the boundary between a transparent and an opaque zone, the other electroluminescent diode is either within an opaque zone or within a transparent zone and will accordingly supply a constant signal.